Technical Abstract: Mycosphaerella graminicola is the haploid ascomycete that causes Septoria tritici blotch, one of the most important diseases of wheat worldwide. This pathogen is phylogenetically distinct from other fungi that have been sequenced and is hemibiotrophic; early infection is biotrophic, followed by a switch to nectrophic growth just prior to symptom expression. More than 15 genes for resistance have been identified and named in wheat, some of which have been shown to interact in a gene-for-gene relationship. However, the trigger for the switch from biotrophic to nectrotrophic growth of the pathogen and the mechanisms of resistance in the host are not known. To better understand the biology of this pathosystem, the genome of the pathogen was sequenced completely by filling in the gaps in an 8.9' draft sequence. The essentially finished sequence contains 18 chromosomes from telomere to telomere, plus five fragments. Four of the five fragments contain telomeres so they presumably make up two additional chromosomes for a total of 20. A comparative bioinformatics analysis of M. graminicola with seven other sequenced fungal genomes revealed that M. graminicola possessed fewer enzymes than expected for degrading plant cell walls. Analyses of grass-infecting pathogens versus those from other hosts indicated that the suites of cell wall-degrading enzymes were tailored to break down the cell wall compositions of their particular hosts. The frequency of transposable elements in the genome of M. graminicola was intermediate between those of other sequenced fungi. Many long (> 10 kb) retrotransposons were identified in the finished genome compared to the draft sequence, indicating the need for finishing of other fungal genomes. Availability of the finished genome for M. graminicola should greatly aid research on this organism and will help to understand its interaction with wheat.